1. Field of the Invention
This invention relates to a system and method for reducing hydrocarbons in wastewater, and in particular, benzene in desalter effluent water and contaminated ground water.
2. Background
Government agencies are providing guidelines of how hazardous wastes shall be disposed of and limits to the amount of hazardous wastes that may be released to the atmosphere. The Environmental Protection Agency has prepared a regulation, entitled "National Emission Standards for Hazardous Air Pollutants" (NESHAPS), that provides that refinery wastewater shall have the benzene count reduced before it is released from the refinery. Desalter effluent water and other water streams of many refineries have benzene counts far in excess of the regulation limit.
The desalter effluent water is used to interact with crude oil in one or more stages to remove salts from the crude oil. This water-oil interaction results in benzene and other hydrocarbons becoming part of the desalter effluent water composition and raising the benzene level above the allowable regulation limits. The ground water around and under a refinery may be contaminated with benzene and other hydrocarbons from oil spills and leakages within the refinery facilities. This ground water also can have a benzene count that exceeds the allowable limit.
With this regulation in effect, refineries may no longer just dump their desalter effluent water or other hydrocarbon-contamined water streams. If the refineries do so, they face stiff fines and penalties as set forth in the NESHAPS regulation for harming the environment.